You must have something in your LQ that is putting a constant drain on the battery, causing it to discharge when it's not in use. If you connect an amp meter in series with the B+ terminal, you should see a draw of xxx amount of amps. If you open one circuit breaker at a time inside your power center, you can determine which circuit is causing the drain. Once that is determined, by checking the various devices on that circuit, you can determine by their usage, which one is causing the parasitic drag on the battery.

Until that is trouble shot, determined and corrected, the best thing you can do for the battery's longevity, is to disconnect the B+ lead from the battery terminal (s) and hooking up a battery tender to maintain its charge. If the battery is allowed to completely discharge, particularly in cold weather, it can be completely ruined in a short amount of time. It must have a charge to not freeze in the winter.

Electric welding in the presence of electronic devices, can certainly damage any component that is hit with a large surge in amperage. As was stated, if the welding was not properly grounded, the breakers were opened and the battery was disconnected before any welding was started, you may have some electrical malfunctions from fried equipment.

This happens sometimes in body shops, when automobiles are not properly prepared prior to welding. It can happen on any surface that is used for a ground for various electrical devices, such as a trailer's frame.